Hard Logic Brain Teaser Question

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Hard Logic Brain Teaser Question

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There is an island where people are not allowed to communicate with each other. There are total 200 people out of which, 100 have green eyes while 100 have black eyes. But no one knows their own eyes color as there is no mirror available on the island. Also, they are not aware of how many people with n colored eyes are there. They don't even know that there are only two color set of eyes. But they can observe and analyze other people's eyes.

There is a catch to the things. It is a rule that if anybody is able to deduce the color of his own eyes and he is right, he will be free and can leave the island.

On a certain day, an outsider visits the island and tells the people that he has seen someone with green eyes. What will happen now?

This puzzle is quite similar to the cheating husbands puzzle. The same logic applies here.

After the announcement, if there is only one person with green eyes, he will observe everyone and will come to the conclusion that he himself has green eyes.

If two persons have green eyes, they will see everyone and find out that there is one person with green eyes. So they will expect him to leave. But if no one leaves on that day, on the next day both of them will understand that they both have green eyes and will leave the island.

Thus if you keep going like this or apply the rules of induction, you will find that since there are 100 green eyed people on that island, all of them will leave the island on the 100th day after the announcement.

A strange tradition is followed in an orthodox and undeveloped village. The chief of the village collects taxes from all the males of the village yearly. But it is the method of taking taxes that is interesting.

The taxes paid in the form of grains and every male should pay equal pounds corresponding to his age. In simpler terms, a man aged 10 years will have to pay 10 pounds of grains and a 20 years old will be paying 20 pounds of grain.

The chief stands on a riser containing 7 different weights next to a large 2 pan scale. As per the interesting custom, the chief can only weigh using three of the seven weights.

In such a scenario, can you calculate what must be the weights of the seven weights each and who is the oldest man the chief can measure using those weights?

You have been given three jars of 3 liters, 5 liters and 8 liters capacity out of which the 8 liters jar is filled completely with water. Now you have to use these three jars to divide the water into two parts of 4 liters each.

Four stupid friends meet each other after long time.They are so stupid that they start talking about their suits

* There were a total of eight suits, two in each color, black, brown, pink and white.
* Each friend owned two suits.
* No friend had two suits of the same color.
* Ganpat don't have a white suit.
* Harish don't have a black suit, but did have a brown one.
* One of the friends had a white suit and a pink suit and another friend had a brown suit and a pink suit.
* Manoj had a white suit.
* Tarun had a pink suit, but don't have a brown one.

We know that Christanio Ronaldo tells the truth on only a single day of the week. If the statement on day 1 is untrue, this means that he tells the truth on Monday or Tuesday. If the statement on day 3 is untrue, this means that he tells the truth on Wednesday or Friday. Since Christanio Ronaldo tells the truth on only one day, these statements cannot both be untrue. So, exactly one of these statements must be true, and the statement on day 2 must be untrue.
Assume that the statement on day 1 is true. Then the statement on day 3 must be untrue, from which follows that Christanio Ronaldo tells the truth on Wednesday or Friday. So, day 1 is a Wednesday or a Friday. Therefore, day 2 is a Thursday or a Saturday. However, this would imply that the statement on day 2 is true, which is impossible. From this we can conclude that the statement on day 1 must be untrue.

This means that Christanio Ronaldo told the truth on day 3 and that this day is a Monday or a Tuesday. So day 2 is a Sunday or a Monday. Because the statement on day 2 must be untrue, we can conclude that day 2 is a Monday.

So day 3 is a Tuesday. Therefore, the day on which Christanio Ronaldo tells the truth is Tuesday.

A couple had to take shelter in a hotel for they could not proceed their journey in the rain. Having nothing to do at all, they started playing cards. Suddenly there was a short circuit and the lights went off. The husband inverted the position of 15 cards in the deck (52 cards normal deck) and shuffled the deck.

Now he asked his wife to divide the deck into two different piles which may not be equal but both of them should have equal number of cards facing up. There was no source of light in the room and the wife was unable to see the cards.

For a certain amount of time, she thought and then divided the cards in two piles. To the husband’s astonishment, both of the piles had equal number of cards facing up.

The answer is very simple. All she had to do is take the fifteen cards from the top and reverse them. This would make another pile out of that and there will be two piles - one of 15 cards and one of 37 cards. Also both of them will have the same number of inverted cards.

Just think about it and if the mathematical explanation will help you understand better, here it is.
Assume that there were p inverted cards initially in the top 15 cards. Then the remaining 37 cards will hold 15-p inverted cards.
Now when she reverses the 15 cards on the top, the number of inverted cards will become 15-p and thus the number of inverted cards in both of the piles will become same.

A pack of cards has 52 cards. You are blindfolded. Out of 52, 42 cards are facing down while 10 are facing up. You have been asked to divide this pack of cards into two decks - so that each deck contains an equal number of face up cards. Remember, you are blindfolded.

Take 10 number of cards in a new deck and change their face direction. For example- You create a new deck of 10 cards and out of 10, 3 faces up in the new deck. So remaining 7 faces up are in the old deck. But hey! while creating the new deck you reversed the face direction of new cards. So actually the 3 cards which were facing up are actually face down in the new deck while 7 faces up.